This invention relates to adjuvants and vaccines. More particularly, this invention relates to adjuvants and vaccines based on polyoxypropylene-polyoxyethylene block polymers.
Freund's discovery that the immunogenicity of antigens could be potentiated by emulsifying an aqueous antigen solution with mineral oil alone or with mineral oil and M. tuberculosis, formed the basis of the concept of using a secondary material to increase a subject's humoral and cell-mediated immune responses to an antigen. An essential component of Freund's complete and incomplete adjuvant is mineral oil. This component plays a central role in effecting an increased humoral response to the antigen. However, mineral oil is only acceptable for use in research circumstances. The mycobacteria in complete Freund's adjuvant are essential for significantly enhanced cellular immunity.
Though little attention was initially paid to the role the surfactant may play in Freund's incomplete or complete adjuvant, subsequent research has indicated that in several instances a surfactant may demonstrate adjuvant properties in and of itself. A number of naturally occurring surface active agents such as the lipid A portion of endotoxin of gram negative bacteria and trehalose dimycolate of mycobacteria are among the most potent adjuvants of these naturally occurring surfactants. A constituent of mammalian cells, the phospholipid lysolecithin also has been shown to have adjuvant activity. (B. Arnold et al, Eur. J. Immunol., 9:363-366 (1979).)
In addition, several synthetic surfactants, for example, dimethyldioctadecyl ammonium bromide (DDA) and certain polyoxypropylene-polyoxyethylene block polymers have been reported as having adjuvant activity. (See H. Snippe et al, Int. Archs. Allergy Appl. Immun., 65:390-398 (1981). In addition, R. Hunter et al, have reported in the Journal of Immunology, 127:1244-1250 that polyoxypropylene-polyoxyethylene block polymers, when used as the surfactant component of an oil-in water based adjuvant formulation, increase antibody formation to BSA in mice.
While these natural and synthetic surfactants demonstrate a certain degree of adjuvanticity, results so far published demonstrate that, except for one specific test methodology for DDA, none of the surfactants when used alone matches the immunopotentiating activity found when using complete or incomplete Freund's adjuvant. However, it is not possible to use either Freund's incomplete or complete adjuvant for general vaccination purposes because both mineral oil and mycobacteria have deleterious side effects when injected subcutaneously as a result of which it has not been authorized for domestic animal or human use by governmental regulatory agencies. Mineral oil is limited to use in experimental animals.
However, there is a substantial need for some means of potentiating the immunogenicity of antigens. This is particularly true because virus subunit and other protein antigens are now being prepared by recombinant DNA technology. Moreover, naturally occurring or synthetic peptide fragments from larger proteins known to be antigenic are being administered rather than whole protein or a mixture of materials containing the whole protein.
To elicit useful immune responses, antigenic proteins and haptens must be administered with some type of adjuvant. Neither mineral oil nor mycobacteria can be used, as noted above. Glycopeptides should be able to provide the needed immunopotentiation, but these materials are most effective when presented to the subject as an emulsion. Since mineral oil may not be used due to its toxicity, an alternative emulsion-forming material is needed for administering antigens.
It has now been found that when immunopotentiating glycopeptides and an antigen are confected with a non-toxic polyoxypropylene-polyoxyethylene block polymers and a multiphase stabilizing amount of a glycol ether-based non-toxic surfactant, the immunogenicity of the antigen is increased in the same manner and to the same degree as when mineral oil is used. It has been found that the block polymer is critical to achieving an immune response but that a maximal response is most effectively achieved only when the multiphase system is stabilized by some detergent such as a non-ionic glycol ether-based surfactant. The presence of a metabolizable oil may enhance the effectiveness of these formulations as well. Because the polyoxypropylene-polyoxyethylene block polymers and glycol ether surfactants are non-toxic, this adjuvant formulation may be safely used as a vehicle for enhancing the immunogenicity of antigens administered to birds and mammals.